Genotype

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An organism's genotype is all of the genes it has. The characteristics that an organism displays are called its phenotype.

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Some characteristics, e.g. dimples, are controlled by only by genes. This can just be one gene, or quite often the characteristic is controlled by several genes working together e.g. eye colour.

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Other characteristics, e.g. scars, are controlled only by environmental factors. They don't have anything to do with genes and are caused by things like how and where you live.

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There are also characteristics that are controlled by both genes and environmental factors. For example, weight - if both your parents are skinny, you'll probably be skinny unless you live an unhealthy lifestyle.